Plasma coating methods and apparatus are known. For example, one patent relates to a method and apparatus for plasma flame spray coating material onto a substrate. The patent discloses a method and apparatus for plasma flame spray coating material onto a substrate by means of passing a plasma forming gas through a nozzle electrode, and passing an arc forming current between the nozzle electrode and a rear electrode to form a plasma effluent. The method includes introducing coating material into the plasma effluent, passing the plasma effluent axially through a wall shroud extending from the exit of said nozzle electrode, and forming a flame shroud for the plasma effluent. The coating is thereby applied to the substrate.
One area where such technology is particularly advantageous is in connection with repairing thermal barrier coatings on various aircraft components, particularly gas turbine engines and their components. For example, thermal barrier coatings on turbine vanes and the like can become damaged due to a number of factors such as high operating stress, high cycle fatigue, and foreign object damage. Typically, repairing thermal barrier coatings require the component to be masked in areas where the material transfer is not required and/or not desired. Furthermore, the component typically must be removed from the engine and repaired in a dedicated facility such as an aircraft engine manufacturing plant or repair shop. Prior art methods and apparatus required masking the component and repairing the thermal barrier coatings in dedicated facilities because the coating equipment was large and not portable and spray pattern was too wide to accurately control the coating process. It would be desirable to improve the accuracy of spray coating devices so that masking and the like would not be required, as well as permitting hand spray coating repairs in the field of operation.